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Second workshop meeting on hydrotreating catalysts Louvain-la-Neuve, Belgium, 29–30 October 1984
403 MEETING
REPORT
SECOND WORKSHOP MEETING ON HYDROTREATING CATALYSTS Louvain-la-Neuve, Belgium, 29-30 October 1984 This two-day workshop meetiing was held under the auspices of the Contact Group "Catalysis" of the FNRS/NFWO as well as the Socigte Chimique de Belgique. It was organised by Dr. F. Delannay and his coworkers of the Groupe de Physico-Chimie de Mine)raleet de Catalyse of the Universite Catholique de Louvain. About one hundred participants representing industrial, governmental and university laboratories were present; besides a majority of contributions from laboratories in Western Europe, the results of studies carried out in Hungary and the U.S.A. were also presented. The proceedings of the workshop, in the form of the texts of all the 24 papers presented, were made available at the start of the meeting as Vol.93 (Nos.8-9) of Bull. Sot. Chim. Beiges. An invited introductory lecture on outstanding problems of HDS catalysis was delivered by Dr. P.C.H. Mitchell whereas an invited review paper by Dr. H. Topsoe dealt with recent developments with respect to the "CO-MO-S model". A number of papers dealing with catalytic functionalities and reaction mechanisms can be generalised as follows. In sulphided supported CO-MO catalysts, different active sites are involved for different reactions such as HDS of dibenzothiophene, hydrogenation of naphthalene and HDN of indole. Addition of Ni to MO-A1203 affects the number of thiophene HDS sites rather than the nature of those sites and the primary function of the Ni-MO-S phase is to stabilise a very disordered MoS phase. Sulphided Co-MO-Al 0 catalysts are more active for HDS (2-methylthiopheieand dibenzothiophene) th&3Ni-Mo-Al 0 and Ni-W-Al 0 catalysts which, however, have a higher activity for HDO (ShJnol and o-creso$3 ) and HDN (aniline and o-toluidine), most probably because they are also the better catalysts for aromatic ring hydrogenation (ethylbenzene and o-xylene). The hetero-atoms in planar molecules (such as dibenzothiophene and dibenzofurane) are less reactive than those in comparable folded molecules (such as thioxanthane and xanthane) which, within a series of homologues, have similar reactivities; this is probably because the adsorbed state of the planar molecules is more stabilised than that of the folded ones. The physico-chemical and catalytic properties of unsupported (and related) catalysts were described in a number of communications, The HDS of dibenzothiophene and the hydrogenation of biphenyl over unsupported MoS2 and WS2 were proposed to be texture-insensitivereactions. The results of TPR and TPD studies of co-precipitated CO-MO sulphide powders showed that their behaviour with respect to hydrogen is strongly affected by the presence of both Co and MO. In specifically prepared Ni-Mo sulphide catalysts, a rather unstable mixed Ni-MO-S phase containing mobile sulphur species and resembling MoS2 from the crystallographic point of view was reported to be formed at certain N1 contents; its presence was supposed to result in an increased activity for the HDS of dibenzothiophene and the hydrogenation of biphenyl. Mossbauer analysis showed that CO-MO sulphide catalysts (HSP type) may contain three other Co species besides Co S and CO-MO-S phases; the latter phase proved to be rather stable in in a high8y-reducing atmosphere. The results of a DTA study of HSP-type sulphided CO-MO, Ni-Mo, Co-W and Ni-W catalysts suggested the formation of a mixed Co(Ni)MO(W)-S phase in all these systems: Ni appeared to be the best promoter for the hydrogenation of biphenyl. Iron sulphide supported on a relatively inert Support such as carbon was reported to be far more active for the HDS of thiophene-than alumina-supported iron sulphide and its activity appeared to be even higher than that of MoS2 on carbon. The characterisation of sulphide catalysts via chemisorption of probe molecules was the subject of four presentations. There now seems to be a consensus of opinion on observation that the chemisorption of oxygen is generally related to the dispersion of the active phase and not to any specific reaction site. lnfrared studies of adsorbed NO, combined with observations made with other techniques such as AEM, MES and EXAFS, have shown that the catalytically active
apmm-
Volume
14No.I-3
- February 1985
404 CO-MO-S and Ni-MO-S phases present in CO-MO and Ni-Mo HDS catalysts consist of Co and Ni atoms at the edges of MoS2; these studies also showed that substantial promotion of the HDS activity can only be achieved when both the MoS edge dispersion and the coverage of these MoS2 redges by Co or Ni are high. I$ was suggested that CO adsorption on reduced and sulphided MO-Al 0 leads to formation of 23 Mo4+-CO and Mo2+-CO adsorption complexes respectively. Finally,*infrared analysis of adsorbed CO was demonstrated to be a very useful method of studying the the CO-MO interaction in sulphided Co-MO-Al 03 catalysts. One session comprising of three papers was 2evoted to some aspects of the sulphidation of Co-MO-alumina catalysts. The sulphidation of the various MO and Co species present in oxidic Co-MO-Al203 catalysts have successfully been studied by means of temperature-programmedsulphiding (TPS); it was found for instance that MO in Co-MO-Al203 sulphides in the same way as that in MooA and that the sulphidation of Co strongly depends on the calcination temperature. depending on the sulphidation temperature, two types of CO-MO-S can be formed: when compared (using HREM, IR, XRD, DOC and thiophene HDS) with the low-temperature CO-MO-S form, the high-temperature structure of CO-MO-S has a much higher coverage of the by Co of the MoS2 sites, a weaker interaction with the alumina support and a considerably higher HDS activity per Co atom. Activation with a 15% H S in H mixture between 673 and 8OOK was observed to give optimum HDS active ,$y; the*concentration of active sites per unit surface area of the active phase (HREM, XPS, ISS and DOC) and their intrinsic thiophene HDS activity seemed to be independent of the activation temperature up to 1073KThe last set of communications was concerned with the nature of the active sites. Based on the existence of small MoS patches and the assumption that active sites are exclusively situated at ti4 e MoS2 edges, a geometrical model of the active phase present in (un)promoted (un)supported hydrotreating catalysts was put forward. Small first-, second- and third-row transition metal sulphide particles supported on a carbon surface appeared to have the same catalytic properties for HDS rections as bulky unsupported particles and superior catalysts were found to preserve a high degree of metallic character (low binding energy shift) under sulphiding conditions; the reasons for Me-C catalysts being more active than MO-Al203 was discussed. The Hougen-Watson model with a fixed number of active sites appeared to account more satisfactorily for the influence of H and H S on the number of thiophene HDS and hydrogenation sites present in szlphidez Co-MO-A1203 catalysts than did the Hougen-Watson model with interconverting sites. From the results of a quantum-chemical study, it was concluded that thiophene is most probably chemisorbed in a one-point vertical position on a MoS*,edge-site having two sulphur vacancies and that C4H4 is an intermediate product In the HDS process. V.H.J. de Beer
Eindhoven (The Netherlands) Accepted 18th December 1984
BOOK REVIEW i Microprocessor Programming and Applications for Scientists and Engineers, by R.R. Smardzewski, Elsevier, Amsterdam and New York, 1984, xiv t 354 pages, Dfl 98.00, US$ 37.75, ISBN o-444-42407-5. This book is written for all those researchers and their students who wish to automate their laboratory experiments. It provides specific guidelines on how to design such equipment automation starting from fundamental concepts. The book is based on the popular 6502 microprocessor which is used in a variety of micro-computing systems such as Apple, Acorn, Atari, BBC and Commodore. All 35 programming examples throughout the text, however, were generated and tested on a Rockwell AIM 65 micro, a system which features easily accessible interface facilities. A very systematic course is presented, no prior background in microprocessors
m-am-
Volume 14 No. l-3
- February 1995
REPORT
SECOND WORKSHOP MEETING ON HYDROTREATING CATALYSTS Louvain-la-Neuve, Belgium, 29-30 October 1984 This two-day workshop meetiing was held under the auspices of the Contact Group "Catalysis" of the FNRS/NFWO as well as the Socigte Chimique de Belgique. It was organised by Dr. F. Delannay and his coworkers of the Groupe de Physico-Chimie de Mine)raleet de Catalyse of the Universite Catholique de Louvain. About one hundred participants representing industrial, governmental and university laboratories were present; besides a majority of contributions from laboratories in Western Europe, the results of studies carried out in Hungary and the U.S.A. were also presented. The proceedings of the workshop, in the form of the texts of all the 24 papers presented, were made available at the start of the meeting as Vol.93 (Nos.8-9) of Bull. Sot. Chim. Beiges. An invited introductory lecture on outstanding problems of HDS catalysis was delivered by Dr. P.C.H. Mitchell whereas an invited review paper by Dr. H. Topsoe dealt with recent developments with respect to the "CO-MO-S model". A number of papers dealing with catalytic functionalities and reaction mechanisms can be generalised as follows. In sulphided supported CO-MO catalysts, different active sites are involved for different reactions such as HDS of dibenzothiophene, hydrogenation of naphthalene and HDN of indole. Addition of Ni to MO-A1203 affects the number of thiophene HDS sites rather than the nature of those sites and the primary function of the Ni-MO-S phase is to stabilise a very disordered MoS phase. Sulphided Co-MO-Al 0 catalysts are more active for HDS (2-methylthiopheieand dibenzothiophene) th&3Ni-Mo-Al 0 and Ni-W-Al 0 catalysts which, however, have a higher activity for HDO (ShJnol and o-creso$3 ) and HDN (aniline and o-toluidine), most probably because they are also the better catalysts for aromatic ring hydrogenation (ethylbenzene and o-xylene). The hetero-atoms in planar molecules (such as dibenzothiophene and dibenzofurane) are less reactive than those in comparable folded molecules (such as thioxanthane and xanthane) which, within a series of homologues, have similar reactivities; this is probably because the adsorbed state of the planar molecules is more stabilised than that of the folded ones. The physico-chemical and catalytic properties of unsupported (and related) catalysts were described in a number of communications, The HDS of dibenzothiophene and the hydrogenation of biphenyl over unsupported MoS2 and WS2 were proposed to be texture-insensitivereactions. The results of TPR and TPD studies of co-precipitated CO-MO sulphide powders showed that their behaviour with respect to hydrogen is strongly affected by the presence of both Co and MO. In specifically prepared Ni-Mo sulphide catalysts, a rather unstable mixed Ni-MO-S phase containing mobile sulphur species and resembling MoS2 from the crystallographic point of view was reported to be formed at certain N1 contents; its presence was supposed to result in an increased activity for the HDS of dibenzothiophene and the hydrogenation of biphenyl. Mossbauer analysis showed that CO-MO sulphide catalysts (HSP type) may contain three other Co species besides Co S and CO-MO-S phases; the latter phase proved to be rather stable in in a high8y-reducing atmosphere. The results of a DTA study of HSP-type sulphided CO-MO, Ni-Mo, Co-W and Ni-W catalysts suggested the formation of a mixed Co(Ni)MO(W)-S phase in all these systems: Ni appeared to be the best promoter for the hydrogenation of biphenyl. Iron sulphide supported on a relatively inert Support such as carbon was reported to be far more active for the HDS of thiophene-than alumina-supported iron sulphide and its activity appeared to be even higher than that of MoS2 on carbon. The characterisation of sulphide catalysts via chemisorption of probe molecules was the subject of four presentations. There now seems to be a consensus of opinion on observation that the chemisorption of oxygen is generally related to the dispersion of the active phase and not to any specific reaction site. lnfrared studies of adsorbed NO, combined with observations made with other techniques such as AEM, MES and EXAFS, have shown that the catalytically active
apmm-
Volume
14No.I-3
- February 1985
404 CO-MO-S and Ni-MO-S phases present in CO-MO and Ni-Mo HDS catalysts consist of Co and Ni atoms at the edges of MoS2; these studies also showed that substantial promotion of the HDS activity can only be achieved when both the MoS edge dispersion and the coverage of these MoS2 redges by Co or Ni are high. I$ was suggested that CO adsorption on reduced and sulphided MO-Al 0 leads to formation of 23 Mo4+-CO and Mo2+-CO adsorption complexes respectively. Finally,*infrared analysis of adsorbed CO was demonstrated to be a very useful method of studying the the CO-MO interaction in sulphided Co-MO-Al 03 catalysts. One session comprising of three papers was 2evoted to some aspects of the sulphidation of Co-MO-alumina catalysts. The sulphidation of the various MO and Co species present in oxidic Co-MO-Al203 catalysts have successfully been studied by means of temperature-programmedsulphiding (TPS); it was found for instance that MO in Co-MO-Al203 sulphides in the same way as that in MooA and that the sulphidation of Co strongly depends on the calcination temperature. depending on the sulphidation temperature, two types of CO-MO-S can be formed: when compared (using HREM, IR, XRD, DOC and thiophene HDS) with the low-temperature CO-MO-S form, the high-temperature structure of CO-MO-S has a much higher coverage of the by Co of the MoS2 sites, a weaker interaction with the alumina support and a considerably higher HDS activity per Co atom. Activation with a 15% H S in H mixture between 673 and 8OOK was observed to give optimum HDS active ,$y; the*concentration of active sites per unit surface area of the active phase (HREM, XPS, ISS and DOC) and their intrinsic thiophene HDS activity seemed to be independent of the activation temperature up to 1073KThe last set of communications was concerned with the nature of the active sites. Based on the existence of small MoS patches and the assumption that active sites are exclusively situated at ti4 e MoS2 edges, a geometrical model of the active phase present in (un)promoted (un)supported hydrotreating catalysts was put forward. Small first-, second- and third-row transition metal sulphide particles supported on a carbon surface appeared to have the same catalytic properties for HDS rections as bulky unsupported particles and superior catalysts were found to preserve a high degree of metallic character (low binding energy shift) under sulphiding conditions; the reasons for Me-C catalysts being more active than MO-Al203 was discussed. The Hougen-Watson model with a fixed number of active sites appeared to account more satisfactorily for the influence of H and H S on the number of thiophene HDS and hydrogenation sites present in szlphidez Co-MO-A1203 catalysts than did the Hougen-Watson model with interconverting sites. From the results of a quantum-chemical study, it was concluded that thiophene is most probably chemisorbed in a one-point vertical position on a MoS*,edge-site having two sulphur vacancies and that C4H4 is an intermediate product In the HDS process. V.H.J. de Beer
Eindhoven (The Netherlands) Accepted 18th December 1984
BOOK REVIEW i Microprocessor Programming and Applications for Scientists and Engineers, by R.R. Smardzewski, Elsevier, Amsterdam and New York, 1984, xiv t 354 pages, Dfl 98.00, US$ 37.75, ISBN o-444-42407-5. This book is written for all those researchers and their students who wish to automate their laboratory experiments. It provides specific guidelines on how to design such equipment automation starting from fundamental concepts. The book is based on the popular 6502 microprocessor which is used in a variety of micro-computing systems such as Apple, Acorn, Atari, BBC and Commodore. All 35 programming examples throughout the text, however, were generated and tested on a Rockwell AIM 65 micro, a system which features easily accessible interface facilities. A very systematic course is presented, no prior background in microprocessors
m-am-
Volume 14 No. l-3
- February 1995